


snap decisions and a dragon displaced

by Gintrinsic



Category: Avatar: The Last Airbender, Fullmetal Alchemist: Brotherhood & Manga
Genre: Alternate Universe, Azula's dimension zapping lightning babey!, Crossover, Dimension Travel, Gen, The Gate of Truth, and everyone's favorite flame alchemist dad, is probably to blame? idk, ozai isn't actually in this fic but I am a huge fan of the Terrible Parent tag, starring the world's most awkward firebender
Language: English
Status: Completed
Published: 2020-07-13
Updated: 2020-07-13
Packaged: 2021-03-04 18:01:46
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,568
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25250536
Author URL: https://archiveofourown.org/users/Gintrinsic/pseuds/Gintrinsic
Summary: Despite Uncle's warning, Zuko doesn't manage to divert Azula's lightning away from his heart. The next thing he knows, he's waking up to the roaring horror of what has to be a furious spirit in the middle of a forest. At least he's not the only firebender nearby. Though, truthfully, the other guy's a bit clueless.
Relationships: Zuko (Avatar) & Roy Mustang
Comments: 52
Kudos: 393





	snap decisions and a dragon displaced

**Author's Note:**

> Couldn't decide if I wanted to write something for atla or fma: brotherhood so I chose both lol. Honestly not sure if this has been done before (I was too afraid to search the crossover before writing), but now I desperately need more Zuko and Mustang interactions in my life. 
> 
> Set in the FMA universe, after Gluttony escapes capture.

_“If you let the energy in your own body flow, the lightning will follow it. You must create a pathway from your fingertips, up your arm, to your shoulder, then down into your stomach. The stomach is the source of energy in your body, it is called the Sea of Chi. From the stomach, you direct it up again and out the other arm. The stomach detour is critical; you must not let the lightning pass through your heart, or the damage could be deadly. If you’re lucky, you will never have to use this technique at all.” - Uncle Iroh, episode "Bitter Work"_

Zuko knew what it felt like to burn.

Even after the searing, hissing heat of Ozai’s shameful lesson, desperation had branded him into shapes unrecognizable to the childhood left behind—desperation to restore his honor, to be accepted, to be _worth_ something.

Zuko’s was a fuse tirelessly relit. His anger had simmered like a thing alive, a persistent flutter that wanted to be more. He thrived on that heat, and it helped him _survive_ ; the arctic depths, Zhao’s twisted plots, the undertaking of a one-hundred-year search others mocked as futile. And then, when his inner fire had dwindled to the barest ember after joining the Avatar’s group, when his blood felt cold with draconian lethargy, he had sought heat elsewhere, refusing to be tempered; dragon’s fire had been a different kind of blaze, a kaleidoscope of pure warmth that seeped its way into his very bones.

His entire life, he’d traded one fire for another. He was a true son to his country, a creature of Agni’s bright forge.

So Zuko knew what it felt like to burn. But being struck by the spitting rat-viper that was Azula’s lightning?

He’d never burned quite like this.

—

“Mustang!” the Homunculus screeched gutturally, and trees snapped in the distance against the monster’s stumbling charge.

The feeling of being chased left chills down Mustang’s spine, multifocal counterpoints to the hot ringing in his ears. If Hawkeye had been any slower in her pursuit, her shots any less wonderfully reliable, he’d have been fresh meat moments ago. As it was, one of her bullets had left a spray of Gluttony’s blood across the right side of Mustang’s face, and he could feel as it alternated between stickiness and spectral evaporation.

The undergrowth was treacherous to navigate, and branches tore at his jacket. As Mustang sprinted into a small clearing, pain blossomed sharply across his right side; he gasped, stumbling to his knees and inwardly cursing Lust for the umpteenth time. He supposed this was too much to ask of his body so soon after the stunt in the Fifth Laboratory, but damn if this wasn’t the time for weakness. Gritting his teeth, Mustang tried to fight the rolling waves of nausea that accompanied the pain. He focused on inhaling steadily through his nose, but every breath sounded too loud, too much like a target, like _prey_. He had to get up, he _had to move_ , he—

A shadow stirred just ahead, rustling bushes as it crept closer, and suddenly in the darkness there was the distinct, unnatural glow of two golden eyes. _Another homunculus_ , Mustang reasoned, feeling dread even as it warred with furious, calculating resolve.

He wasn’t going down like this, not when he still had so much to do. He _wasn’t_.

Without conscious thought, Mustang snapped his thumb and middle finger together, igniting a spark whose base nature he fed, fed, fed. And like the eager rush of a hungry tide, fire surged forward in a rolling, destructive wave. It was wild, a white-tipped assault meant for consumption more than precision, and Mustang fully expected to smell roasting flesh.

Only belatedly, as the figure finally stepped into the moonlight, did Mustang see the teenage, human features belonging to those eyes, as well as the defining scar heavily decorating one.

Dismay settled in Mustang’s stomach, made it drop like a weight. Suddenly, he was back in Ishval, back amongst the oppressive heat and scalding sand and sun-bleached stone, facing a young guerrilla who stared with vacant resignation moments before orders came down, and it was sickeningly easy to fall back into the beast of that place, to keep raised a shaking, gloved hand and acknowledge only the ugly, primordial urge to survive.

Mustang watched his fire arc toward its victim and didn’t have time to wonder if he had acted too rashly.

There was a quiet rush, the intimate sound of oxygen being consumed, when the teenager hurriedly thrust his hands forward as though in prayer; and the fire, met with a determined sweep of two arms, split like a ribbon cut down its middle, tongues of flame dying in the air as though gently doused.

Mustang’s stare was incredulous. He had never seen one of his alchemical attacks so easily deflected, as if the heat had been gently dissipated.

This—this wasn’t good. There was no way of knowing what this new threat was capable of, and Mustang’s back was exposed to the rest of the forest in the worst of ways. He sucked in a breath and kept both hands ready, prepared to fight despite the intensifying pain in his right side.

Readjusting his stance, the teenager scowled fiercely. The front of his robe and undershirt appeared freshly tattered, and his exposed chest sported an impressive amount of pink, spiderwebbing scar tissue. “Enough,” he demanded imperiously, fists raised. “Where am I? Where’s Azula?” 

Mustang narrowed his eyes, trying to place the name. “Is that another homunculus?”

Confusion briefly colored the teenager’s expression before the scowl returned. “ _Where am I?_ ” he demanded again, taking a step forward.

“Outside of Central. Now stay back,” Mustang growled, and something in his tone must’ve conveyed the deadliness of his warning because the teenager didn’t advance again.

“Central? I have to get back to the palace,” he stressed, making absolutely no sense. “I—I don’t know what happened, but I know my destiny, _our_ destiny.”

Mustang didn’t even know where to start with any of this, but at least the teenager didn’t seem intent on retaliating. He strained to pick up another sound in the forest, some indication that this was a stalling tactic for something much worse, but the surrounding woods were eerily quiet. There was no indication of how close Gluttony was; hopefully, the others were managing to avoid his new, barbaric appetite. “Look, I don’t know of any palace in Amestris, and I certainly don’t give a damn about any kind of destiny your kind is interested in, so why don’t you tell me what you’re really after? **”**

“My kind?” the teenager asked. Then, with a glare, he half-shouted, “I am not a traitor! If anything, I’m the only one in the royal family who’s truly loyal to the citizenry.”

Royal family? Was he Xingese nobility, like Ling? If so, then what the hell was he doing out here? Was this all some bizarre misunderstanding, or was the homunculi hierarchy way more complicated than any of them had ever realized? Nothing was adding up. Regardless, if the “kid” kept yelling like that, they were bound to draw Gluttony’s attention sooner rather than later. Mustang needed to get out of the forest—and fast, his injury reminded him with a pang. “Whose side are you on?” he asked, risking a quick glance upward to get his bearing.

“The Avatar’s,” the teenager answered, raising his chin proudly.

Again, that didn’t ring in any bells. Mustang hated feeling so ignorant. “Who?”

Apparently baffled, the teenager repeated, “Who? _Who is the Avatar_? You can’t be serious. Have you been living under a rock?” Before Mustang could offer a retort, the teenager spared a glance around, seemingly no longer as cautious of the alchemist. “This isn’t the Fire Nation, is it?” he asked, sounding confused. “The climate is all wrong. And your clothes are… unusual.”

“Fire Nation?” Mustang repeated, ignoring the jab at his outfit to get answers. “What are you talking about?”

The look he got this time was nothing short of disbelieving, and if there had been any doubt about the teenager’s claim to royalty before, the supercilious, almost patronizing climb of his single brow dispelled it. “What am _I_ talking about? You’re a firebender! Even if your fire feels strange.”

Mustang’s left eye twitched at the additional insult. “Well, aren’t you a delightful conversationalist,” he gritted. He was half-tempted to snap his fingers again, to see if the teenager could fend off even pinpoint combustion—and the intensity of that facial scar told Mustang he _couldn’t—_ but he didn’t want to risk provoking a fight unless he had to at this point.

“You’re clearly of Fire Nation descent,” the teenager insisted, gesturing to Mustang’s features, which—what? “Even if you’re from the colonies, you should still know—Ugh, this doesn’t matter! I have to get back to Katara, assuming… assuming this is even the same day.” He pressed a palm to his chest and grimaced, something like grief flashing across his face before he fought it back.

“Look, kid,” Mustang cautioned, “if you’re truly human, if this isn’t some piss-poor attempt to get me to let my guard down, this isn’t a safe place to talk.”

“Of course I’m human. What else would I be?” the teenager retorted hotly, just as a monstrous bellow shook the trees around them and scores of earth were gouged out by some invisible swallow a short distance away.

“Oh,” the teenager concluded lamely. His shock appeared genuine, and Mustang made the abrupt decision to grab him by the arm and shove, potential poor choices be damned.

“Run!” he ordered, but the teenager stubbornly ignored him.

“What about you?”

“Don’t worry about me,” Mustang griped, annoyed by the lack of obedience but unwilling to waste any more time. He withdrew chalk from his coat pocket and drew a hasty array on the ground before performing a transmutation. Within moments, clumps of dirt morphed into the vague shape of a hunched-over lookalike. Ignoring the teenager’s startled exclamation—“Was that _earthbending_? Who _are_ you?”—Mustang threw his coat and gloves over the newly shaped earth. “Now _run_ ,” he ordered again.

This time, Mustang took his own advice, and the teenager was quick to follow. Ignoring the way each step brought fresh agony, he sprinted toward the direction of the house, desperately willing the others to be okay. Moments later, another bellow shook the trees, and Gluttony’s bloodcurdling, enraged denial suggested that the bait hadn’t gone to waste.

“Is that a spirit?” the teenager yelled, looking appropriately alarmed. “What did you do to make it so mad?”

Mustang flashed him a look out of the corner of his eye. “It’s Gluttony,” he answered shortly, winded.

As they approached the tree line, Mustang’s strength seemed to leave him all at once. Stumbling badly, he was surprised when the teenager gripped him by the shoulder.

“I can help,” he offered plainly, and Mustang was once again left questioning the circumstances surrounding the kid.

They had barely cleared the forest when the distinct clank of metal announced the Elric brothers. Hawkeye was close behind, looking largely unruffled by the whole affair.

“Colonel!” Fullmetal exclaimed, sounding more relieved than he’d probably ever admit, though he eyed the stranger with no little suspicion. The teenager, for some reason, seemed torn between staring at Al’s entire body and Edward’s… hair? “Who’s Scar two-point-oh?”

“Ed!” Al chastised, just as the teenager blushed and complained, “Hey!”

“We can talk later,” Hawkeye advised sharply, nodding toward the house where a car sat idling. With smoothness Mustang frankly envied, she slipped one of his arms across her shoulders and effectively separated Mustang from the teenager.

The last trek to the car felt like it lasted forever. Every noise from the forest made them tense, but they made it to the car without incident. While Al assisted Ling with Lan Fan, Ed stood to the side, looking wary of the teenager. Or maybe he was just jealous of his height, Mustang thought with amusement.

The teenager, for his part, hardly seemed to be bothered by their recent sprint through the woods. He stared at the car, clearly impressed for some reason. “I haven’t seen a model like this,” he muttered. “It’s so… sleek.”

“A real damn sportscar,” Dr. Knox snapped from the driver’s seat. “Let’s get the hell out of here!”

With help from Hawkeye, Mustang slid into the front seat. As soon as he was situated, Hawkeye turned a pistol toward the mysterious teenager. “One wrong move,” she warned coolly.

The teenager stared at the gun without any sense of gravity, but he seemed to grasp the sentiment quickly enough. “Uh, sure.” Careful not to jostle Lan Fan, he slid into the middle of the backseat, and Hawkeye was quick to follow.

Then Fullmetal, Al and Ling announced that they were going to stay behind to fight. It was some of the most ridiculous, self-sacrificing bullishness Mustang had ever heard, and some of the bravest. Despite the way his vision was beginning to darken at the edges with every flare of pain, Mustang felt a tremendous amount of respect for those three boys.

As Knox peeled out of the driveway, Mustang glanced over his shoulder with a quiet grunt. “What’s your name?” he asked the teenager, who appeared uneasy at the question. After a long, awkward pause, he took a breath and returned Mustang’s stare resolutely.

“It’s Zuko.”

Mustang didn’t recognize the name, and that lack of recognition seemed to drain some of Zuko’s confidence. “How did you stop my flame alchemy?” he asked, ignoring Hawkeye’s quiet intake of breath and Dr. Knox’s white-knuckled grip on the steering wheel.

Zuko appeared surprised by the question. “Alchemy?” he repeated, and something about his casual ignorance deeply unnerved Mustang, almost as much as the unnatural brightness of his eyes. The color was close to Fullmetal's, he noted belatedly.

“You put out the fire.”

“I used basic firebending,” Zuko explained quietly, as if Mustang were the one saying vague, unsettling things. There was a moment of silence, broken only by the crunch of dirt under the tires, before Zuko asked, “Do you have a map?”

Dr. Knox rooted around in the glove compartment and tossed back an old, printed copy before anyone could protest; Mustang decided he was too tired to care about the poor strategic value in educating a potential antagonist, but Hawkeye scowled appropriately.

Zuko, for his part, peered at the map with slowly increasing distress. He turned it this way and that, then brought it closer to his face. Finally, looking paler than before, he neatly refolded the map before setting it aside.

Mustang was sure that was something to be worried about later. Right now, he couldn’t help but feel guilty about leaving children behind to fight his battle. Putting a hand to his side, he grimly reminded himself that at least in Central, he could begin pulling some strings. It would have to be enough.

In the far distance, the tops of several trees suddenly vanished amid the crackling, red-lit edges of a deep screech. Everyone in the car flinched, but soon the car began clearing a hill and the forest was left behind.

Zuko stared out the window as they drove away, eyes wide with nervousness and awe. “You must’ve been some glutton,” he remarked seriously.

**Author's Note:**

> lmao Mustang thinks Ed is stubborn and difficult to manage? Wait til he gets to know THIS quitting-isn't-in-my-vocabulary asshole!


End file.
